physical geography Physical geography (also known as physiography) is one of the two fields of geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hell ...

, a channel is a type of

landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws ...

consisting of the outline of a path of relatively shallow and narrow body of fluid, most commonly the confine of a river,

river delta A river delta is a landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the ...

strait A strait is a naturally formed, narrowing, typically navigable waterway that connects two larger bodies of water. The surface water generally flows at the same elevation on both sides and through the strait in either direction. Most commonly i ...

strait

. The word is cognate to

canal Canals are waterways channels Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * ...

canal

, and sometimes takes this form, e.g. the

Hood Canal Hood Canal is a fjord forming the western lobe, and one of the four main basins,Bierman, R. B, David R. Montgomery (2014). Key Concepts in Geomorphology. W. H. Freeman and Company Publishers. United States. This site is referred to as the channel head and it marks an important boundary between hillslope processes and fluvial processes. The channel head is the most upslope part of a channel network and is defined by flowing water between defined identifiable banks. A channel head forms as overland flow and/or subsurface flow accumulate to a point where shear stress can overcome erosion resistance of the ground surface. Channel heads are often associated with

colluvium Colluvium (also colluvial material or colluvial soil) is a general name for loose, unconsolidated sediment Sediment is a naturally occurring material that is broken down by processes of weathering Weathering is the deterioration of rocks ...

, hollowss and

landslides The term landslide or, less frequently, landslip refers to several forms of mass wasting Mass wasting, also known as slope movement or mass movement, is the geomorphic process by which soil Soil (often stylized as SOiL) is an American roc ...

Overland flow Surface runoff (also known as overland flow) is the flow of water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it ac ...

is a primary factor in channel initiation where saturation overland flow deepens to increase shear stress and begin channel incision. Overland flows converge in topographical depressions where channel initiation begins. Soil composition, vegetation, precipitation, and topography dictate the amount and rate of overland flow. The composition of a soil determines how quickly saturation occurs and cohesive strength retards the entrainment of material from overland flows. Vegetation slows infiltration rates during precipitation events and plant roots anchor soil on hillslopes. Subsurface flow destabilizes soil and resurfaces on hillslopes where channel heads are often formed. This often results in abrupt channel heads and landslides. Hollows form due to concentrated subsurface flows where concentrations of colluvium are in a constant flux. Channel heads associated with hollows in steep terrain frequently migrate up and down hillslopes depending on sediment supply and precipitation.

Natural channels

Natural channels are formed by

fluvial In geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ap ...

process and are found across the

Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wi ...

Earth

. These are mostly formed by flowing

water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...

water

from the

hydrological cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, describes the continuous movement of water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, ...

, though can also be formed by other fluids such as flowing

lava Lava is magma Magma () is the molten or semi-molten natural material from which all s are formed. Magma is found beneath the surface of the , and evidence of has also been discovered on other and some s. Besides molten rock, magma may al ...

lava

can form

lava channel Slightly eroded lava channel at Stóra-Eldborg undir Geitahlíð, Stóra-Eldborg, Reykjanes peninsula, Reykjanes, Iceland, left over from Holocene eruptions. In the background the respective fissure vents, eruption fissure with craters and behind, ...

s. Channels also describe the deeper course through a

reef A reef is a ridge or shoal A tidal sandbar connecting the islands of Waya and Wayasewa of the Yasawa Islands, Fiji ">Fiji.html" ;"title="Yasawa Islands, Fiji">Yasawa Islands, Fiji In oceanography, geomorphology, and earth sciences, a s ...

reef

sand bar A tidal sandbar connecting the islands of Waya Island, Waya and Wayasewa of the Yasawa Islands, Fiji In oceanography, geomorphology, and earth sciences, a shoal is a natural submerged ridge, Bank (geography), bank, or bar that consists of, or ...

bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface ...

bay

, or any shallow body of water. An example of a river running through a sand bar is the

Columbia Bar The Columbia Bar, also frequently called the Columbia River Bar, is a system of bar (landform), bars and shoals at the mouth of the Columbia River spanning the U.S. states of Oregon and Washington (state), Washington. The bar is about wide and lo ...

—the mouth of the

Columbia river The Columbia River (Upper Chinook Upper Chinook, endonym Kiksht, also known as Columbia Chinook, and Wasco-Wishram after its last surviving dialect, is a recently extinct language of the US Pacific Northwest. It had 69 speakers in 1990, of w ...

. A stream channel is the physical confine of a

stream A stream is a body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official written standard for the No ...

stream

(

river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...

river

) consisting of a

bed A bed is a piece of furniture Furniture refers to movable objects intended to support various human activities such as seating (e.g., chairs, stools, and sofas), eating (table (furniture), tables), and sleeping (e.g., beds). Furniture ...

and

stream bank A man-made lake in Keukenhof with grass banks In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the ...

s. Stream channels exist in a variety of geometries. Stream channel development is controlled by both

and

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...

movement. There is a difference between low

gradient In vector calculus Vector calculus, or vector analysis, is concerned with differentiation Differentiation may refer to: Business * Differentiation (economics), the process of making a product different from other similar products * Prod ...

streams (less than a couple of percent in gradient or slightly sloped) and high gradient streams (steeply sloped). A wide variety of stream

channel typesA wide variety of river and stream channel types exist in limnology, the study of inland waters. All these can be divided into two groups by using the Stream gradient, water-flow gradient as either ''low gradient channels'' for streams or rivers with ...

can be distinguished (e.g.

braided river A braided river, or braided channel, consists of a network of river s separated by small, often temporary, s called s or, in English usage, ''s'' or ''eyots''. Braided streams tend to occur in rivers with high loads and/or coarse grain sizes, and ...

s, wandering rivers, single-thread

sinuous Image:rio-cauto-cuba.JPG, The meandering ''Cauto River, Rio Cauto'' at Guamo Embarcadero, Cuba, is not taking the shortest path downslope. Therefore, its sinuosity index is > 1. Sinuosity, sinuosity index, or sinuosity coefficient of a ...

sinuous

rivers etc.). During

flood A flood is an overflow of water that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide Tides are the rise and fall of sea level Mean sea level (MSL) (often ...

flood

s, water flow may exceed the capacity of the channel and flood waters will spill out of the channel and across the

valley A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over ...

valley

bottom,

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows int ...

or drainage area. Examples of rivers that are trapped in their channels:

Grand Canyon The Grand Canyon (, yuf-x-yav, Wi:kaʼi:la, , ) is a steep-sided canyon A canyon (; archaic British English spelling: ''cañon'') or gorge is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive ...

and

Black Canyon of the Gunnison

. In a larger nautical context, as a geographical place name, the term ''channel'' is another word for

, which is defined as a relatively narrow body of water that connects two larger bodies of water. In this

nautical Seamanship is the art Art is a diverse range of (products of) human activities Humans (''Homo sapiens'') are the most populous and widespread species of primates, characterized by bipedality, opposable thumbs, hairlessness, and intell ...

context, the terms ''strait'', ''channel'', ''sound'', and ''passage'' are synonymous and usually interchangeable. For example, in an

archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster or collection of island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as ...

, the water between

island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as water. Very small islands such as emergent land features on atoll An atoll (), sometimes known as a coral atoll, i ...

island

s is typically called a ''channel'' or ''passage''. The

English Channel The English Channel,, "The Sleeve"; nrf, la Maunche, "The Sleeve" (Cotentinais Cotentinais is the dialect The term dialect (from Latin , , from the Ancient Greek word , , "discourse", from , , "through" and , , "I speak") is used in two ...

is the strait between England and France.

Waterflow channels

The channel form is described in terms of geometry (plan, cross-sections, profile) enclosed by the materials of its bed and banks. This form is under influence of two major forces: water discharge and sediment supply. For erodible channels the mutual dependence of its parameters may be qualitatively described by Lane's Principle (also known as Lane's relationship): the product of the sediment load and bed Bukhara size is proportional to the product of discharge and channel slope.

Nautical channels

It is especially used as a nautical term to mean the dredged and marked lane of safe travel which a cognizant governmental entity ''guarantees'' to have a minimum depth across its specified minimum width to all

vessels

transiting a body of water (''see''

Buoy A buoy (, North America more commonly, but not exclusively ) is a Buoyancy, floating device that can have many purposes. It can be anchored (stationary) or allowed to drift with ocean currents. The etymology of the word is disputed. Types Na ...

Buoy

). The term not only includes the

deep-dredged

ship-navigable parts of an

estuary An estuary is a partially enclosed Coast, coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime envir ...

estuary

or river leading to

port A port is a maritime Maritime may refer to: Geography * Maritime Alps, a mountain range in the southwestern part of the Alps * Maritime Region, a region in Togo * Maritime Southeast Asia * The Maritimes, the Canadian provinces of ...

port

facilities, but also to lesser channels accessing

boat A boat is a watercraft Watercraft, also known as water vessels or waterborne vessels, are vehicles A vehicle (from la, vehiculum) is a machine A machine is any physical system with ordered structural and functional properties. It m ...

boat

port-facilities

such as

marina A marina (from Spanish Spanish may refer to: * Items from or related to Spain: **Spaniards, a nation and ethnic group indigenous to Spain **Spanish language **Spanish cuisine Other places * Spanish, Ontario, Canada * Spanish River (disambig ...

marina

s. When dredged channels traverse

bay mud Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuary, estuaries, which are normally in temperate regions that have experienced cyclica ...

or sandy bottoms, repeated dredging is often necessary because of the unstable subsequent movement of benthic soils.''History of the Waterways of the Atlantic Coast of the United States''
,

USACE The United States Army Corps of Engineers (USACE) is an formation of the that has three primary mission areas: engineer regiment, military construction, and civil works. The day-to-day activities of the three mission areas are administered ...

USACE

, January 1983 Responsibility for monitoring navigability conditions of ''navigation channels'' to various port facilities varies, and the actual maintenance work is frequently performed by a third party. Storms, sea-states, flooding, and seasonal sedimentation adversely affect

navigability A body of water ( Lysefjord) in Norway Norway ( nb, ; nn, ; se, Norga; smj, Vuodna; sma, Nöörje), officially the Kingdom of Norway, is a Nordic countries, Nordic country in Northern Europe whose mainland territory comprises the ...

. In the U.S., navigation channels are monitored and maintained by the

United States Army Corps of Engineers , colors = , battles = , battles_label = Wars , website = , commander1 = LTG Scott A. Spellmon , commander1_label = Comma ...

(USACE), although dredging operations are often carried out by private contractors (under USACE supervision). USACE also monitors water quality and some remediation. This was first established under the

Rivers and Harbors Act of 1899 The Rivers and Harbors Appropriation Act of 1899 is the oldest federal environmental law in the United States The United States of America (USA), commonly known as the United States (U.S. or US), or America, is a country Contiguous United St ...

and modified under acts of 1913, 1935, and 1938. For example, the USACE developed the

Intracoastal Waterway The Intracoastal Waterway (ICW) is a inland waterway along the Atlantic Seaboard, Atlantic and Gulf of Mexico coasts of the United States, running from Boston, Massachusetts, southward along the Atlantic Seaboard and around the southern tip of ...

, and has the

Mississippi Valley Division The United States Army Corps of Engineers Mississippi Valley Division (MVD) is responsible for the Corps water resources programs within 370,000-square-miles of the Mississippi River Valley, as well as the watershed portions of the Red River of t ...

responsible for the

Mississippi River The Mississippi River is the second-longest river and chief river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and b ...

from the Gulf to

Cairo, Illinois Cairo ( ) is the southernmost city in the U.S. state of Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It has the List of U.S. states and territories by GDP, fifth lar ...

, the North Atlantic Division for New York Harbor and

Port of Boston The Port of Boston ( AMS Seaport Code: 0401, UN/LOCODE: US BOS) is a major seaport located in Boston Harbor and adjacent to the Boston, Massachusetts, City of Boston. It is the largest port in Massachusetts as well as being one of the principal po ...

, and the South Pacific Division for

Port of Los Angeles The Port of Los Angeles, also promoted as "America's Port", is a seaport managed by the Los Angeles Harbor Department, a unit of the City of Los Angeles. It occupies of land and water along of waterfront and adjoins the separate Port of Long Bea ...

and

Port of Long Beach The Port of Long Beach, also known as the Harbor Department of the City of Long Beach, is a container port in Singapore A container port or container terminal is a facility where Intermodal container, cargo containers are transshipped bet ...

. Waterways policing as well as some emergency spill response falls under

United States Coast Guard The United States Coast Guard (USCG) is the maritime security, search and rescue, and maritime law enforcement, law enforcement military branch, service branch of the United States Armed Forces and one of the country's eight Uniformed services ...

jurisdiction, including inland channels serving

s like

Saint Louis

hundreds of miles from any coast. The various state or local governments maintain lesser channels, for example former

Erie Canal The Erie Canal is a canal Canals are waterways channels Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a nar ...

Extraterrestrial channels

Extraterrestrial natural channels are found elsewhere in the

Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

than the

and the longest and widest of which are the

outflow channels Image:Kasei Valles topo.jpg, 300px, Kasei Valles, seen in MOLA elevation data. Flow was from bottom left to right. North is up. Image is approx. across. The channel system extends another south of this image to Echus Chasma. Outflow channels are ...

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury (planet), Mercury. In English, Mars carries the name of the Mars (mythology), Roman god of war and is often referred to ...

Mars

and the channels of

Venus Venus is the second planet from the Sun. It is named after the Venus (mythology), Roman goddess of love and beauty. As List of brightest natural objects in the sky, the brightest natural object in Earth's night sky after the Moon, Venus can ...

Venus

many of which are tens of kilometres wide (the network of channels flowing from

Argyre Planitia Argyre Planitia is a plain located within the impact basin Argyre in the southern highlands of Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, being larger than only Mercury (planet), Mercury. ...

on Mars for example is 8000 km in length and the Baltis Vallis Venus is 7000 km compared to the 6,650 km Nile, the largest active channel on Earth). The exact formation of these large ancient channels is unknown although it is theorised that those on Mars may have been formed due to catastrophic flooding and on Venus by lava flow. In

planetary science Planetary science (or more rarely, planetology) is the scientific study of planets (including Earth), Astronomical object, celestial bodies (such as Natural satellite, moons, Asteroid, asteroids, Comets on Fire, comets) and planetary systems (in p ...

the term "

rille Rille (German for 'groove') is typically used to describe any of the long, narrow depressions in the surface of the Moon The Moon is Earth's only natural satellite. At about one-quarter the diameter of Earth (comparable to the wi ...

" is sometimes used for similar formations found on

The Moon The Moon is Earth's only natural satellite. At about one-quarter the diameter of Earth (comparable to the width of Australia (continent), Australia), it is the largest natural satellite in the Solar System relative to the size of its plane ...

and

Mercury Mercury usually refers to: * Mercury (planet) Mercury is the smallest planet in the Solar System and the closest to the Sun. Its orbit around the Sun takes 87.97 Earth days, the shortest of all the Sun's planets. It is named after the Roman g ...

Mercury

that are of inconclusive origin. Channels have also been recently discovered on

Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictional ...

. The Saturnian moon has the only known liquid-filled channels in the Solar System other than Earth, the largest of which ( Vid Flumina) is 400 km in length. These are believed to be formed from flowing hydrocarbons in the hypothesized methanological cycle.pg 71. Large Rivers: Geomorphology and Management. Avijit Gupta. John Wiley & Sons, 2007

References

{{coastal geography

Bodies of water {{See also, Limnology Compare to :Landforms and :Wetlands Bodies of water may exist within land areas or within other bodies of water and may be natural, man-made or a combination. Water Physical geography Hydrography Natural resources, +Water A ...

Coastal and oceanic landforms Fluvial landforms Nautical terminology Water streams